KR101392114B1 - Spark Plug - Google Patents

Abstract

An object of the present invention is to provide a spark plug having excellent load life performance even when subjected to impact or vibration. The spark plug of the present invention is characterized in that a plurality of bent portions formed in the insulated body so as to be received in the yoke so as to bend properly are closer to the inner circumferential surface of the insulator at three or more positions and such bent portions are not shifted in the radial direction of the yoke .

Description

Spark plug {SPARK PLUG}

The present invention relates to a spark plug used for ignition of an internal combustion engine, and more particularly to a spark plug having a resistor inside.

BACKGROUND ART A spark plug used for ignition of an internal combustion engine such as an automobile engine generally has a tubular metal shell, a tubular insulator disposed in an inner hole of the metal shell, And a ground electrode having one end connected to the tip end side of the metal shell and the other end facing the center electrode to form a spark discharge gap. A spark plug in which a resistor is provided between a center electrode and a metal terminal in a shaft hole is also known for the purpose of preventing the generation of propagation noise.

This resistor usually comprises a mixture of a glass powder and a conductive material such as carbon black powder or metal powder. However, since the resistance of the resistor is not so large, it is difficult to directly bond the metal terminal or the center electrode made of metal. Therefore, it is common practice to improve the bonding strength by disposing a sealing layer containing a relatively large amount of metal powder between the metal terminal and the resistor and between the center electrode and the resistor.

However, in recent years, internal combustion engines such as automobiles are required to have high output and high efficiency, and development of miniaturized spark plugs is required for designing a free engine and downsizing of the engine itself. In order to miniaturize the spark plug, it is inevitable that the insulator is made small in size. On the other hand, in order to secure desired characteristics such as the mechanical strength of the insulator, a predetermined thickness dimension in the radial direction is required. Therefore, in order to cure the insulator small, the hole diameter of the insulator must be small. However, when the hole diameter of the insulator is made small, the diameter of the resistor and the sealing layer is also narrowed. As a result, the junction between the resistor and the sealing layer is weakened, and when shock or vibration acts on the spark plug, cracks are generated in the interface between the resistor and the sealing layer, and as a result, the load life performance is deteriorated.

Regarding such a problem, for example, in claim 1 of patent document 1, "... Wherein the diameter D of the conductive glass sealing layer is in the range of 3.3 mm or less and the joint surface of the conductive glass sealing layer and the resistor is formed in a curved shape. According to the present invention, it is possible to provide a spark plug which is excellent in resistance to vibration (vibration-resistant motion) and resistive load life characteristics by reinforcing the adhesion between the resistor and the conductive glass sealing layer, Quot;).

Patent Document 1: Japanese Patent Application Laid-Open No. 2009-245716

An object of the present invention is to provide a spark plug excellent in load lifetime performance even when subjected to impact or vibration.

As means for solving the above problems,

(1) an insulator having a shaft yoke extending in the axial direction,

A center electrode held at one end side of the shaft yoke,

A metal terminal having a receiving portion accommodated in the shaft hole and held at the other end side of the insulator,

And a connecting portion for electrically connecting the center electrode and the metal terminal in the shaft hole, the spark plug comprising:

When the side on which the metal terminal in the sole yoke is held is the rear end side in the axial direction,

And a connecting member which forms the connecting portion between the outer peripheral surface of the distal end portion of the receiving portion and the inner peripheral surface of the insulator,

In a cross-sectional image perpendicular to the axis taken at intervals of 0.5 mm from the rear end of the receiving portion to the rear end position where the connecting member is present from the rear end toward the front end,

The center of the receiving portion in the section image S _n at the n-th (n is a natural number) cross-section from the rear end side of the receiving portion is _denoted by a _n , the center of the shaft yoke is _denoted by O _n , a _n and O _n that the straight line passing through L _n, the inner diameter of the shaft hole 2R _n, the outer diameter 2r of the receiving portion P _n, a point _n and the distance of the point O _n H _{aon, aon} H ≥0.8 (R _n- r _n ), the point a _n is _defined as a point A _n ,

The cross-sectional image S ₁ to the circumference of the axis around the straight line L ₁ that the O ₁ 45 ° rotated straight line in which the straight line L _{1 +,} -45 ° rotated straight line in which the straight line L ₁ in _-, the straight line L _{1 +} X ₊ and the axial plane and the straight line L ₁ including the _- X plane and containing the axis _- the surrounding Sy are four regions by the inner peripheral surface of the insulator and _{T 1, T 2, T 3} , T ₄ ,

Points to a row in a particular one area selected from the area T ₁ ~T ₄ A _m ~ point A _{(m + k)} in the presence of (m and k are natural numbers), the group (群) these set B _{m, y} (where y is a natural number and means that it is the y-th set when counted from the rear end side of the receiving portion)

wherein the maximum value of y is at least 3 and at least two of the groups B _{m , y} are present in two regions at symmetrical positions selected from T ₁ to T ₄ .

In a preferred form of (1) above,

(2) the A _s and cross-sectional images including (where point A _s represents the point A _n of the first from the rear end side of the blood receiving portion), the point A _e (where point A _e is the blood receiving portion The distance D between the curved portions, which is the distance in the axial direction of the sectional image including the last point A _n when counted from the rear end side, is 5 mm or more,

(3) the group B _{m , y} is present in at least three regions selected from T ₁ to T ₄ ,

(4) the maximum value of y is at least 4,

(5) the group B _{m , y} exists in all the regions T ₁ to T ₄ ,

(6) the maximum value of y is at least 5,

(7) When the inner diameter of the shaft hole in the portion where the distal end is disposed is a diameter of a middle diameter portion, the diameter of the middle diameter portion is 2.9 mm or less,

(8) the distance D between the bent portions is not less than 7 mm,

(9) The distance D between the bent portions is 10 mm or more.

The spark plug of the present invention is characterized in that the maximum value of y is at least 3 and at least two of the groups B _{m and y} are present in the two regions at symmetrical positions selected from T ₁ to T ₄ , It is possible to provide a spark plug having excellent load life performance. In other words, since a plurality of bent portions in which the portions to be received are appropriately bent are close to three or more places on the inner peripheral surface of the insulator, and these bent portions exist without being deviated in the radial direction of the shaft yoke, It is possible to prevent the receiving portion from swinging with a plurality of bent portions which are close to the inner circumferential surface of the receiving portion. Therefore, the fluctuation of the receiving portion is not transmitted to the connecting portion, so that the occurrence of cracks in the interface between the resistor forming the connecting portion and the first sealing layer and the second sealing layer can be suppressed. As a result, The resistance does not rise rapidly. Therefore, it is possible to provide a spark plug having excellent load life performance even when subjected to impact or vibration.

The spark plug of the present invention has a distance in the axial direction between a sectional image including a point A _s and a sectional image including a point A _e of at least 5 mm. Therefore, the bending portions at both ends of the plurality of bending portions are spaced apart from each other by a predetermined distance or more in the axial direction, so that the receiving portion can be further restrained from swinging. As a result, the load lifetime performance after the shock or vibration is further improved.

When the diameter of the middle diameter portion of the spark plug of the present invention is 2.9 mm or less, the effect of improving the load life performance in the case of shock or vibration is further enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional explanatory view of a spark plug which is an embodiment of a spark plug according to the present invention
2 is a cross-sectional explanatory view of a main portion of a spark plug according to an embodiment of the present invention;
3 is an explanatory diagram of a cross-sectional image S ₁ photographed at a line segment I ₁ J ₁ of the spark plug shown in FIG. 2
Fig. 4 is an explanatory diagram of a cross-sectional image in which a cross-sectional image S _n photographed at a line segment I _n J _n of the spark plug shown in Fig. 2 is arranged in order from the rear end side
Fig. 5 is an explanatory diagram of a main part between I ₁ J ₁ and I ₁₃ J _{13 in} Fig. 2
6 is a process drawing showing an example of a process of the spark plug manufacturing method according to the present invention
7 is a top view explaining a case _where a cross-section image S _n of a spark plug, which is another embodiment of the spark plug according to the present invention,
8 is a top view explaining a case _where a cross-section image S _n of a spark plug, which is another embodiment of the spark plug according to the present invention,
Fig. 9 is a top view explaining a case _where a cross-section image S _n of a spark plug, which is another embodiment of the spark plug according to the present invention,

Fig. 1 shows a spark plug which is an embodiment of the spark plug according to the present invention. Fig. 1 is an explanatory diagram of a whole section of a spark plug 1, which is an embodiment of a spark plug according to the present invention. 1, the side on which the center electrode is held is referred to as the tip direction of the axis O, the upper side of the paper, that is, the side on which the metal terminal is held The rear end direction of the axis O will be described.

The spark plug 1 includes an insulator 3 having a shaft hole 2 extending in the direction of the axis O, a center electrode 4 held at the tip end side of the shaft hole 2, (6) for electrically connecting the center electrode (4) and the metal terminal (5) in the shaft hole (2), and a connection terminal And a ground electrode (8) having one end joined to the end surface of the metal shell (7) and the other end opposing to the center electrode (4) via a gap do.

The metal shell 7 has a substantially cylindrical shape and is formed to receive and hold the insulator 3. A screw portion 9 is formed on the outer circumferential surface of the metal shell 7 in the front end direction and the spark plug 1 is mounted on a cylinder head of an internal combustion engine not shown using the screw portion 9. [ The metal shell 7 may be formed of a conductive steel material, for example, a low carbon steel. It is preferable that this screw portion 9 is made to be M12 or less for small-scale curing.

The insulator 3 is held on the inner peripheral portion of the metal shell 7 with a talc 10 or a packing 11 interposed therebetween. The shaft hole 2 of the insulator 3 has a small diameter portion 12 for holding the center electrode 4 at the tip end side of the axis O and a small diameter portion 12 for holding the center electrode 4 at the connection portion 6 and the metal terminal 5 Receiving portion 19 which is continuous to the leading end side of the small diameter portion 12 and which has an inner diameter larger than the inner diameter of the small diameter portion 12 and adjacent to the small diameter portion 12 via the step portion 13 And a middle diameter portion (14). The insulator 3 is fixed to the metal shell 7 in a state in which the end in the tip direction of the insulator 3 protrudes from the end face of the metal shell 7. [ The insulator 3 is preferably a material having mechanical strength, thermal strength, electrical strength and the like. As such a material, for example, a ceramic sintered body mainly composed of alumina can be given.

The center electrode 4 is accommodated in the small diameter portion 12 of the shaft hole 2 and is attached to the step portion 13 of the shaft hole 2 at a flange portion 17 and is held insulated with respect to the metal shell 7 in a state in which the tip end protrudes from the distal end surface of the insulator 3. The center electrode 4 is preferably made of a material having thermal conductivity and mechanical strength and is formed of, for example, a Ni-based alloy such as Inconel (trade name). The center of the center electrode 4 may be formed of a metal material having excellent thermal conductivity such as Cu or Ag.

The ground electrode 8 is formed of, for example, a substantially square prism. The ground electrode 8 is connected to the distal end surface of the metal shell 7 at one end thereof. The ground electrode 8 is bent at approximately L- The shape and structure of the center electrode 4 are designed so as to face the front end of the center electrode 4 via a gap. The ground electrode 8 is formed of the same material as the material for forming the center electrode 4.

The noble metal tips 29 and 30 formed of a platinum alloy and an iridium alloy may be provided on the surface of the center electrode 4 and the ground electrode 8 opposite to each other. The noble metal tip may be provided on only one of the electrodes 8. [ In this type of spark plug 1, noble metal tips 29 and 30 are provided on both the center electrode 4 and the ground electrode 8, and between the noble metal tips 29 and 30 A spark discharge gap g is formed.

The metal terminal 5 is a terminal for applying a voltage for externally applying a spark discharge between the center electrode 4 and the ground electrode 8 to the center electrode 4. The metal terminal 5 has an outer diameter larger than the inner diameter of the shaft hole 2 and is exposed from the shaft hole 2 so that a part of the flange portion of the insulator 3 on the rear end side end in the direction of the axis O And a substantially columnar receiving portion 19 which is continuous from the end side end face in the axial direction O direction of the exposed portion 18 in the front end direction and is accommodated in the shaft hole 2, I have. The receiving portion 19 includes a fixed portion 25 having a concave-convex surface on the distal end portion 20 of the axis O and a fixed portion 25 disposed on the rear end side of the axis O and adjacent to the exposed portion 18 (22). The fixing portion 25 and the body portion 22 are accommodated in the middle-diameter portion 14. The outer peripheral surface of the fixing portion 25 has a concavo-convex structure formed by, for example, a knurling process. Thus, the fixing portion 25 of the spark plug of this type is knurled, The adhesion between the metal terminal 5 and the connecting portion 6 is improved. As a result, the metal terminal 5 and the insulator 3 are firmly fixed. The metal terminal 5 is made of, for example, low-carbon steel or the like, and a Ni metal layer is formed on the surface thereof by plating or the like.

The connecting portion 6 is disposed between the center electrode 4 and the metal terminal 5 in the shaft hole 2 and electrically connects the center electrode 4 and the metal terminal 5. [ The connecting portion 6 has a resistor 26 and prevents the generation of propagation noise by the resistor 26. [ The connecting portion 6 has a first sealing layer 23 between the resistor 26 and the center electrode 4 and a second sealing layer 24 between the resistor 26 and the metal terminal 5 The first sealing layer 23 and the second sealing layer 24 seal the insulator 3 and the center electrode 4 and the metal terminal 5 to each other.

The resistor 26 is formed of a material such as glass powder such as soda borosilicate glass, ceramic powder such as ZrO ₂ , non-metal conductive powder such as carbon black, and / or metal powder such as Zn, Sb, Sn, And a resistance material formed by sintering the resistor composition. The resistance value of the resistor 26 is usually 100? Or more.

The first sealing layer 23 and the second sealing layer 24 may be composed of a sealing material formed by sintering a sealing powder containing a glass powder such as a sodium borosilicate glass or a metal powder such as Cu and Fe. The resistance values of the first sealing layer 23 and the second sealing layer 24 are usually several hundreds of ohms or less.

Since the first sealing layer 23 and the second sealing layer 24 contain a larger amount of metal components than the resistor 26, they are disposed between the resistor 26 and the center electrode 4 and the metal terminal 5 , Thereby increasing the bonding strength between the two. Hereinafter, the resistor and the sealing powder forming the connecting member and the connecting portion 6, collectively referred to as the resistor and the sealing material constituting the connecting portion 6, are collectively referred to as a connecting portion forming powder.

2 is a cross-sectional explanatory view for explaining a characteristic portion of the spark plug of the present invention. Therefore, the spark plug shown in Fig. 2 mainly shows an insulator and a metal terminal, and a member, a metal shell, and the like disposed at the tip end side of the metal terminal are omitted.

The spark plug of the present invention is a spark plug in which a portion to be received 19 is bent in a wave form and a plurality of It has a bent part. From the interface F between the exposed portion 18 and the receiving portion 19 to the rear end position E where the connecting member is present from the interface between the exposed portion 18 and the held portion 19 at 0.5 mm intervals, (e. g., TOSCANER-32250μhd) when a cross-section image taken S _n that is orthogonal to the axial line by the cross-sectional image S _n of the spark plug of the present invention has the following features:

The line segment I ₁ J ₁ in FIG. 2 represents the position in the axial direction O of the sectional image S ₁ photographed first from the rear end side of the receiving portion 19. In this embodiment, a total of 13 sectional images S _n are photographed up to the sectional image S ₁₃ at a position within 0.5 mm on the rear end side of the rear end position E of the connecting member. Further, S _n indicates that the sectional image is taken at the n-th time from the rear end side of the receiving portion 19.

Therefore, in the spark plug of this embodiment, n is a natural number of 1 to 13, the cross-sectional image is therefore along the axial direction up to 0.5㎜ interval, the blood receiving portion 19, the rear end (F) that is a line segment I ₁ J of ₁ to the rear end position E where the connecting member exists is not less than 6 mm and less than 6.5 mm from the line segment I ₁ J ₁ to the line segment I ₁₃ J ₁₃ .

The distance EF from the rear end F of the receiving portion 19 to the rear end position E where the connecting member exists in the spark plug of the present invention is preferably 15 mm to 70 mm. At this time, the sectional image S _n is obtained by 15 / 0.5 (cut off the decimal point) + 1 (pieces) = 31 (pieces) to 70 / 0.5 (cut off the decimal point) + 1 (pieces) = 141 (pieces). For convenience of explanation, FIG. 2 shows the spark plug of the embodiment in which the distance EF is smaller than 15 mm.

Figure 3 is an explanatory diagram of the cross-section image taken according to the line segment S ₁ I ₁ J ₁ of the spark plug indicated in Fig.

The center of the receiving portion 19 in the sectional image S ₁ is a point a ₁ , the center of the shaft hole 2 is a point O ₁ , the straight line passing the point a ₁ and the point O ₁ is a straight line L ₁ , (2) the outer diameter of the inner diameter of 2R _1, the blood receiving portion (19) 2r _1, the point a ₁ and the distance of the point O ₁ H _ao1 of,

_{H ao1 ≥0.8 (R 1 -r 1} )

And the point of time of a ₁ satisfy the relationship a point A _1.

Distance of the point a ₁ is not in a position satisfying the above formula, the point a ₁ and the point O ₁ is an insulator (3), the inner peripheral surface 31 and blood receiving portion 19, the outer peripheral surface 34 of the case, which matches And the point a ₁ is apart from the point O ₁ by a distance of 80% or more of (R ₁ -r ₁ ). The outer circumferential surface 34 of the receiving portion 19 contacts the inner circumferential surface 31 of the insulator 3 when the point a ₁ is distant from the point O ₁ by a distance R ₁ -r ₁ . When the blood receiving portion 19 is bent, in close proximity to the inner peripheral surface 31 of the insulator 3, a point a ₁ exists at a position which satisfies the above equation are to the points a ₁ to a point A _1.

In the sectional image S ₁ in this embodiment, as shown in Fig. 3, the point a ₁ is only a little away from the point O ₁ , and the relation of the above expression is not satisfied.

n = 2~13 As with n = 1 even when the work, a point _n, point O _n, define a straight line L _n, 2R _{n, n} 2r, H _aon and, in the cross section image S _n,

H _aon ≥0.8 (R _n -r _n ) ... (One)

The point a _n at the time of satisfying the relation of the point A _n is _defined as a point A _n .

Fig. 4 is an explanatory diagram of a cross-sectional image in which a cross-sectional image S _n photographed at a line segment I _n J _n of the spark plug shown in Fig. 2 is arranged in order from the rear end side. As shown in Fig. 4, in the spark plug of this embodiment, the point a _n in the sectional images S _{2 to} S ₄ , S _{6 to} S ₈ , and S _{10 to} S ₁₂ satisfies the above expression (1) The point a ₂ to the point a ₄ , the point a ₆ to the point a ₈ and the point a ₁₀ to the point a ₁₂ of the receiving portion 19 are set as the point A ₂ to the point A ₄ and the point A ₆ to the point A ₈ , The point a to point a ₁₀ ~ _12.

Next, FIG. 5 shows an explanatory diagram of the main part between I ₁ J ₁ and I ₁₃ J ₁₃ in FIG. 3, the linear cross-sectional image to which a periphery of the rotation axis of 45 ° to a straight line around a line L ₁ the point O ₁ of the S ₁ L _{1 +,} -45 ° rotated straight line in which the straight line L _{1 -} when a, as shown in Fig. 5, the straight lines L ₁₊ and the axis (O) ₊ X plane and the straight line L _1, including _- and the _{insulator-plane} X and containing the axis (O) T ₄ , T ₂ , T ₃ , and T ₄ are surrounded by the inner circumferential surface 31 of the base 3, respectively. In this embodiment, T ₁ , T ₂ , T ₃ , and T ₄ are set in turn to the right, with T ₁ being the area in which the point a ₁ exists.

A particular one area selected from the area T ₁ ~T _4, point A _m ~ successive points A _{(m + k)} in the presence of (m and k are natural numbers), such that A _m ~ point A _{(m + k)} is a group B _{m , y} (where y is a natural number and is a y-th set when counted from the rear end of the receiving portion). In other words, the cross-sectional image becomes now called as point A _m by in S _m that a _m is present at a position satisfying the relation of the equation (1), the cross-sectional image than the cross-sectional image adjacent to the front end side S _m S becomes now called point a _{(m + 1)} by the presence in the even that a position of _{(m + 1)} that satisfies the relation of the equation (1) to _{(m + 1),} cross-sectional image S _m ~ sectional image S _{(m + k)} dots in the at least two cross-sectional image to a _m ~ point a _{(m + k)} is that by continuously exist in a position satisfying the above formula (1) a _m ~ point a _{(m + k)} LA now called becomes, and this point a _m ~ point a _{(m + k)} is the presence of a particular one area selected from the area T ₁ ~T _4, such that point a _m ~ a _{(m + k ) Is} the group B _{m , y} .

In, the continuously photographed sectional image S _2, S _3, point A _2, point A _3, point A ₄ is satisfies the above equation (1), one region of the T ₁ on the S ₄ As can be also represented in the 4 Since there exist, this set is group B _{2, 1} . Likewise, since the point A ₆ , the point A ₇ , and the point A ₈ on the consecutively photographed sectional images S ₆ , S ₇ and S ₈ satisfy the above-mentioned formula (1) and exist in one area T ₃ , in group B _6, a _2, a continuously-up cross-sectional images S _10, S _11, point a _10, point a _11, point a ₁₂ will satisfy the equation (1), one region of the T ₁ on the S ₁₂ Since there exist, this set is group B _{10, 3} .

In the spark plug of this embodiment, since there are three groups B _{m , y} , the maximum value of y is 3, and in the two regions T ₁ and T ₃ located at the target position centered on the axis O, B _{2, 1,} and B _{10, 3} , and B _{6, 2} , respectively.

In the conventional structure of the spark plug, when the spark plug is subjected to impact or vibration, only the rear end side of the receiving portion is fixed, and this point serves as a fulcrum, and the receiving portion may swing heavily in the shaft bore. However, in the spark plug of this embodiment, the maximum value of y in the cross-section image S _n is 3, and two of the groups B _{m and y} are symmetrical with respect to the axis O Even if the spark plug 1 is impacted or vibrated, as shown in Fig. 5, the portions 19 to be received are at least divided into groups B _{2 and 1} , groups B _{6 and 2} , groups B _{10 and 3} is the insulator 3-up point b _1, point b _2, point b ₃ to the inner peripheral surface of the in is as a supporting point, the blood receiving portion (19) can be restrained from swinging the remote in the shaft hole (2) . As a result, the water receiving portion 19 oscillates heavily in the shaft hole 2, so that the gap between the first sealing layer 23 and the second sealing layer 24 and the resistor 26, Cracks are generated between the layer 24 and the resistor 26 to prevent the contact failure from occurring. As a result, the resistance of the connection portion 6 does not rise sharply. Therefore, it is possible to provide a spark plug having excellent load life performance even when subjected to impact or vibration.

In addition, the points A _{m to} A _{(m + k)} on the sectional images S _{m to} S _{(m + k)} included in the group B _{m , y} exist at positions satisfying H _aon = (R _n -r _n ) does not, that is, the blood even in the case receiving portion 19, the outer peripheral surface 34 is not present at a position in contact with the inner circumferential surface 31 of the insulator 3 in such as point b ₃ g taken as cross-section image S _n There is a case where a portion other than the portion that is the closest to the inner circumferential surface 31 is the closest. Therefore, if the points A _{m to} A _{(m + k)} included in the group B _{m , y} are separated from the center point O _n of the shaft hole 2 by at least 80% of the distance R ₁ -r ₁ , There is a portion (fulcrum) that comes into contact with the inner circumferential surface 31 of the insulator 3 in the outer peripheral surface 34 of the receiving portion 19 when the receiving portion 19 receives shock or vibration, ) In the direction of the arrow.

In the sectional image S _n of the spark plug of the present invention, the maximum value of y is at least 3, preferably at least 4, particularly preferably at least 5, and varies depending on the length of the terminal, The maximum value of y may be smaller than 20 in general. the larger the value of y means that there are many points where the outer peripheral surface of the receiving portion and the inner peripheral surface of the insulator come into contact with each other when there are a plurality of bent portions formed in the receiving portion close to the inner peripheral surface of the insulator, The more such a point, the more preferable that the receiving portion can be prevented from swinging heavily in the shaft hole.

In the cross-sectional image S _n of the spark plug of the present invention, at least two of the groups B _{m, y} are present in two regions in the symmetrical positions are selected from the area T ₁ ~T _4, groups B _{m, y} is More preferably in three regions, particularly preferably in all regions. The point where the outer circumferential surface of the receiving portion and the inner circumferential surface of the insulator come into contact with each other when the bending portion formed in the receiving portion near the inner circumferential surface of the insulator, that is, the spark plug is impacted, exists at least at the target position about the axis O, It is possible to further inhibit the receiving portion from swinging heavily in the shaft hole.

The spark plug of the present invention, point A _s and cross-sectional images including (where point A _s 1 represents a point A _n of the second from the rear end side of the blood receiving portion 19), point A _e (where, And the distance D between the bent portions which is the distance in the direction of the axis (O) of the sectional image including the last point A _n when the point A _e is counted from the rear end side of the receiving portion 19 is 5 Mm or more, more preferably 7 mm or more, particularly preferably 10 mm or more, and may be a length from the rear end of the receiving portion to the rear end position E of the connecting member. When the distance D between the bend portions is equal to or larger than the predetermined value, the two bend portions at both ends of the bend portions formed in the receiving portion close to the inner peripheral surface of the insulator are spaced apart by a predetermined distance, Can be further suppressed.

In the spark plug of this embodiment, the point A _s is point A ₂ and the point A _e is point A ₁₂ . Because the cross-sectional image is taken with 0.5㎜ interval, the cross-section S ₂ and the image image section S ₁₂ is a distance (D) between the bent portion of the axis (O) direction it is 5㎜.

The spark plug of the present invention is more effective in terms of the load life performance in the case of impact or vibration when the diameter of the middle diameter portion is 2.9 mm or less. The diameter of the middle diameter portion measures the inner diameter of the shaft hole 2 at the portion where the axial direction O end portion of the metal terminal 5 is disposed.

The diameter 2r _n of the receiving portion 19 of the spark plug of the present invention is usually within the range of 70% or more and 97% or less of the inside diameter 2R _n of the shaft hole 2 of the insulator 3.

The spark plug 1 is manufactured, for example, as follows. The following description will focus on the process of installing and fixing the insulator, the center electrode, and the metal terminal in the manufacturing process of the spark plug 1 (see Fig. 6).

First, the center electrode 4, the ground electrode 8, the metal shell 7, the metal terminal 5 and the insulator 3 are formed into a predetermined shape (preparation step) by a known method to form a metal shell 7 is joined to one end of the ground electrode 8 by laser welding or the like (ground electrode bonding step).

The center electrode 4 is inserted into the shaft hole 2 of the insulator 3 and the flange portion 17 of the center electrode 4 is engaged with the step portion 13 of the shaft hole 2, And the center electrode 4 is disposed on the center electrode 12 (first step).

The sealing powder 15 forming the first sealing layer 23, the resistor composition 28 forming the resistor 26 and the sealing powder 16 forming the second sealing layer 24 are successively formed The press pin 32 is inserted into the shaft hole 2 and preliminarily compressed at a pressure of 60 N / mm 2 or more to form the sealing powder 15 and 16 The resistor composition 28 is filled (second step).

The metal terminal 5 is placed so that the tip end portion 20 comes into contact with the sealing powder 16 by inserting the tip end portion 20 of the metal terminal 5 from the rear end side in the shaft hole 2 fair).

Next, while the powder 27 for forming a connection portion is heated for 3 to 30 minutes at a temperature equal to or higher than the glass softening point of the glass powder contained in the sealing powders 15 and 16, for example, 800 to 1000 占 폚, 5 are pushed in until the front end surface of the exposed portion 18 abuts against the rear end surface of the insulator 3 to apply a load to the connecting portion forming powder 27 (fourth step).

Thus, the sealing powders 15 and 16 and the resistor composition 28 constituting the connecting portion forming powder 27 are sintered to form the first sealing layer 23, the second sealing layer 24, and the resistor 26 do. The sealing material constituting the first sealing layer 23 and the second sealing layer 24 is filled in the gap between the flange portion 17 and the shaft hole 2 and the gap between the tip end portion 20 and the shaft hole 2 So that the center electrode 4 and the metal terminal 5 are sealed and fixed in the shaft hole 2. The sectional image S _n is photographed up to the rearmost position where the sealing material exists.

Subsequently, the insulator 3 to which the center electrode 4 and the metal terminal 5 are fixed is assembled to the metal shell 7 to which the ground electrode 8 is bonded (assembling step).

Finally, the tip end portion of the ground electrode 8 is folded toward the center electrode 4 side so that one end of the ground electrode 8 faces the tip end portion of the center electrode 4, and the spark plug 1 is manufactured.

The spark plug of the present invention is characterized in that the composition of the material constituting the metal terminal 5 in the above production method is adjusted, the length and diameter of the portion 19 to be contained are adjusted, Adjusting the exposure length K, which is the length in the axial direction from the front end of the exposed portion 18 to the rear end surface of the insulator 3, changing the hardness (easy to deform) of the sealing powder or resistor composition, And changing the temperature of the hot press in the fourth step.

A spark plug of another embodiment of the spark plug of the present invention will be described with reference to Figs. Figs. 7 to 9 are top views for explaining the case _where all the sectional images S _n are superposed and the sectional image S ₁ is placed on the top. For convenience of explanation, not only the receiving portion 19 and the metal shell 7 in the cross-sectional image superimposed below the sectional image S _{1 are} shown but only the center point a _n or A _n of the receiving portion 19 The position of the water receiving portion 19 with respect to the inner peripheral surface 31 of the shaft hole 2 will be described below. The circle having the minimum radius centering on the axis O shown in Figs. 7 to 9 is a circle having the center point a _n of the receiving portion 19 satisfies the equality in Equation (1) (1) is satisfied when the center point a _n is outside the imaginary line 33, and the above expression (1) is satisfied when the center point a _n is inside the imaginary line 33 It does not satisfy. In other words, when the center point a _n of the receiving portion 19 is apart from the axis O by a distance of 80% or more of (R _n -r _n ), the center point a _n is is present on the outside of the circle containing the other hand, a center point _n is the case that the distance is not less than 80% away from the outside of the axis (O) of (R _n -r _n), a center point is _n, the virtual line 33 As shown in Fig. Further, as described above, a point a _n when the center point a _n exists outside a circle including the line of this virtual line 33 is _defined as a point A _n .

As shown in Figure 7, the cross-sectional image a locus connected to a small value of the order of a point _n in the n S _n is a spiral when viewed in plan. Since the cross-section image S _n is an image photographed at an interval of 0.5 mm, the spark plug of this embodiment has the receiving portion 19 bent in a spiral shape. The point a _n of the receiving portion 19 in the spark plug of this embodiment exists at a position satisfying the above expression (1) is a case that the point a _n is outside the circle including the line of the imaginary line 33 , And the points A ₃ to A ₁₂ satisfy the above expression (1).

Thus, when the area T ₁ ~T point A _m ~ point A _{(m + k)} subsequent to a certain area of which is selected from _4-present as described above, since these sets to the B _{m, y,} and the point A ₄ Point A ₅ is group B _{4, 1} , point A ₆ to point A ₈ are group B _{6, 2} , point A ₉ and point A ₁₀ are group B _{9, 3} , point A ₁₁ and point A ₁₂ are group B _{11, 4} . At this time, the groups B _{4 and 1} are present in the region T ₂ , the groups B _{6 and 2} are present in the region T ₃ , the groups B _{9 and 3} are present in the region T ₄ , and the groups B _{11 and 4} are present in the region T ₁ .

Therefore, in the spark plug of this embodiment, since the number of the groups B _{m , y} is four, the maximum value of y is four, and the group B _{m , y} exists in all the areas T ₁ to T ₄ .

As shown in Fig. 8, the trajectory connecting the points a _n in the cross-sectional image in the order of the smallest value of n is eight-lettered when viewed in plan. Because the cross-sectional image S _n is the image taken by 0.5㎜ gap, the spark plug of this embodiment, the blood receiving portion 19 is bent to approach the inner peripheral surface of the insulator and then, after returning to the vicinity of the axis, the inner peripheral surface of the opposite side of the insulator As shown in Fig. The point a _n of the receiving portion 19 in the spark plug of this embodiment exists at the position satisfying the above expression (1) is the case _where the point a _n is outside the circle including the line of the imaginary line 33 And the points A ₃ to A ₆ and the points A ₉ to A ₁₃ satisfy the above expression (1).

Thus, when the area T ₁ ~T point A _m ~ point A _{(m + k)} subsequent to a certain area of which is selected from ₄ exist described above, since these sets to the B _{m, y,} and that A ₃ Point A ₄ is group B _{3, 1} , point A ₅ and point A ₆ are group B _{5, 2} , point A ₉ to point A ₁₁ are group B _{9, 3} , point A ₁₂ and point A ₁₃ are group B _{12, 4} . At this time, the group B _{3, 1} is present in the area T ₁ , the group B _{5, 2} is in the area T ₂ , the group B _{9, 3} is in the area T ₄ , the group B ₁₂ is in the area T ₃ .

Therefore, in the spark plug of this embodiment, since the number of the groups B _{m , y} is four, the maximum value of y is four, and the group B _{m , y} exists in all the areas T ₁ to T ₄ .

As shown in Fig. 9, the locus connecting the points a _n in the cross-sectional image in the order of the smallest value of n is a star shape when viewed from the plane. S _n is a cross-sectional image, so an image taken with 0.5mm gap, the spark plug of this embodiment, the blood receiving portion 19 is bent to approach the inner peripheral surface of the insulator and then, after returning to the vicinity of the axis, to be close to the inner circumferential surface of the insulator And then repeatedly bent to return to the vicinity of the axis after being further bent. The point a _n of the receiving portion 19 in the spark plug of this embodiment exists at the position satisfying the above expression (1) is the case _where the point a _n is outside the circle including the line of the imaginary line 33 Point A ₂ , point A ₅ , point A ₆ , point A ₉ to point A ₁₁ , point A ₁₃ , and point A ₁₄ satisfy the above expression (1).

Thus, when the area T ₁ ~T point A _m ~ point A _{(m + k)} subsequent to a certain area of which is selected from ₄ exist described above, since these sets to the B _{m, y,} and the point A ₅ Let A ₆ be the group B _{5, 1} , and the points A ₉ through A ₁₁ be the group B _{9, 2} , the point A ₁₃ , and the point A ₁₄ be the group B _13, At this time, the groups B _{5 and 1} are present in the region T ₃ , the groups B _{9 and 2} are present in the region T ₄ , and the groups B _{13 and 3} are present in the region T ₁ .

Therefore, in the spark plug of this embodiment, since the number of the groups B _{m , y} is three, the maximum value of y is 3, and such a group B _{m , y} exists in three regions T ₁ , T ₃ , and T ₄ do.

A spark plug according to the present invention is used as an ignition plug of an internal combustion engine for an automobile, for example, a gasoline engine, and has a screw hole (not shown) provided in a head (not shown) for partitioning a combustion chamber of an internal combustion engine. 9 are screwed and fixed at a predetermined position. The spark plug according to the present invention can be used for any internal combustion engine, but since the spark plug is particularly effective in small-cured spark plugs, the spark plug can be suitably used in an internal combustion engine requiring space saving of the spark plug.

The spark plug according to the present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of achieving the object of the present invention. For example, the spark plug 1 has a fixing portion 25 in which the tip of the metal terminal 5 is knurled, but the surface of the fixing portion 25 has a shape For example, irregular shape, and may be a shape formed by thread cutting or the like. The entire outer peripheral surface and the entire distal end surface of the receiving portion may have a concavo-convex shape, the entire surface of the receiving portion may form a fixed portion, or a part of the surface of the receiving portion may have a concavo-convex shape.

[Example 1]

<Fabrication of spark plug>

The spark plug shown in Fig. 1 was produced according to the above-described manufacturing process. The diameter of the shaft hole of the insulator at the center electrode side tip end portion of the metal terminal (the diameter of the middle diameter portion), the tip end of the exposed portion in the third step described above from by having the length of the axis (O) direction to the rear end of the insulator changes in the (exposure length (K)), making a group B _{m, y} be the group B _{m, y} are present various spark plug region is different from that of did.

To each spark plug by using a micro X-ray CT apparatus (TOSCANER-32250μhd) a 0.5mm pitch to the rear end position of the connecting member there toward the front end from the rear end of the receiving portion P-up the cross-sectional image S _n, as described above, this examined the cross-sectional image be the group B _{m, y} on the basis of S _n and the group B _m, the area (T ₁ ~T _4), between the bend distance (D) which _y is present.

<Evaluation method>

(Load life test)

The manufactured spark plug was placed under an environment of 350 占 폚, and a discharge voltage of 20 kV was applied and discharged 3600 times for 1 minute. The resistance values (R ₀ , R ₁ ) of the resistors of the spark plug before and after this test were measured. The above test was performed 10 times to measure the time at which the average value (R ₁ / R ₀ ) of the resistance value R ₁ after the test to the initial resistance value R ₀ became 1.5 times or more. The longer the time, the better the load life performance And evaluated according to the following criteria. The evaluation results are shown in Table 1.

×: Less than 150 hours

○: 150 hours or more

(Load life test after impact test)

The produced spark plug was subjected to an impact resistance test according to JIS B 8031.

The spark plug after the impact resistance test was tested in the same manner as the load life performance test described above and evaluated according to the following criteria. The evaluation results are shown in Table 1.

1: Less than 5 minutes

1.5: 5 minutes or more but less than 20 hours

2: Less than 20 hours but less than 150 hours

2.5: 150 hours or more and less than 180 hours

3-8.5: added 0.5 points every 20 hours after 180 hours

9: 420 hours or more but less than 450 hours

9.5: 450 hours or more and less than 500 hours

10: 500 hours or more

As shown in Table 1, the spark plug included in the scope of the present invention had satisfactory results both of the load life performance test and the load life performance test after the impact resistance test. On the other hand, the spark plugs outside the scope of the present invention all had satisfactory results of the load life performance test, but the results of the load life performance test after the impact resistance test failed.

1 - spark plug 2 - soccer bru
3 - insulator 4 - center electrode
5 - metal terminal 6 - sealing part
7 - metal shell 8 - ground electrode
9 - Threaded part 10 - Talc
11 - Packing 12 - Small neck
13 - step 14 -
15, 16 - sealing powder 17 - flange portion
18 - Exposed part 19 - Deposited part
20 - tip 22 - body
23 - first sealing layer 24 - second sealing layer
25 - Fixture 26 - Resistor
27 - Powder for forming a connection part 28 - Resistor composition
29, 30 - Precious metal tip 31 - Inner circumference
32 - Press pin 33 - Virtual line
34 -

Claims (9)

An insulator having a shaft yoke extending in the axial direction,
A center electrode held at one end side of the shaft yoke,
A metal terminal having a receiving portion accommodated in the shaft hole and held at the other end side of the insulator,
And a connecting portion for electrically connecting the center electrode and the metal terminal in the shaft hole, the spark plug comprising:
When the side on which the metal terminal in the sole yoke is held is the rear end side in the axial direction,
And a connecting member which forms the connecting portion between the outer peripheral surface of the distal end portion of the receiving portion and the inner peripheral surface of the insulator,
In a cross-sectional image perpendicular to the axis taken at intervals of 0.5 mm from the rear end of the receiving portion to the rear end position where the connecting member is present from the rear end toward the front end,
The center of the receiving portion in the section image S _n at the n-th (n is a natural number) cross-section from the rear end side of the receiving portion is _denoted by a _n , the center of the shaft yoke is _denoted by O _n , a _n and O _n that the straight line passing through L _n, the inner diameter of the shaft hole 2R _n, the outer diameter 2r of the receiving portion P _n, a point _n and the distance of the point O _n H _aon, H _aon ≥0.8 (R _n- r _n ), the point a _n is _defined as a point A _n ,
The cross-sectional image S ₁ to the circumference of the axis around the straight line L ₁ that the O ₁ 45 ° rotated straight line in which the straight line L _{1 +,} -45 ° rotated straight line in which the straight line L ₁ in _-, the straight line L _{1 +} and the plane X ₊ containing the axis the straight line L _{1 -} and the plane X containing the axis _direction of the four regions surrounded Im with the inner circumferential surface of the insulator _{T 1, T 2, T 3} , T ₄ ,
Points to a row in a specific one of the regions selected from the regions T ₁ ~T ₄ A _m ~ point A _{(m + k)} in the presence of (m and k are natural numbers), the group (群) these set B _{m, y} (where y is a natural number, meaning that it is the y-th set when counted from the rear end side of the receiving portion)
wherein the maximum value of y is at least 3 and at least two of the groups B _{m , y} are present in two regions in a symmetrical position selected from T ₁ to T ₄ .
The method according to claim 1,
A point A _s (note that point A _s represents the first point A _n from the rear end side of the receiving portion) and a point A _e (point A _e is a point from the rear end side of the receiving portion And a distance D between the curved portions, which is a distance in the axial direction, of the cross-sectional image including the point A _n of the last one when the cross-sectional image is counted is 5 mm or more.
The method according to claim 1,
And the group B _{m, y} is present in at least three regions selected from T ₁ to T ₄ .
The method according to claim 1,
wherein the maximum value of y is at least 4. &lt; Desc / Clms Page number 13 &gt;
The method according to claim 1,
And the group B _{m, y} is present in all regions T ₁ to T ₄ . The method according to claim 1,
wherein the maximum value of y is at least 5.
The method according to claim 1,
And the diameter of the middle diameter portion is 2.9 mm or less when the inner diameter of the shaft hole in a portion where the tip end portion is disposed is a diameter of a middle diameter portion.
The method of claim 2,
And the distance (D) between the bent portions is 7 mm or more.
The method of claim 2,
And the distance (D) between the bent portions is 10 mm or more.

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